Find the middle element when the numbers in an $n \times n$ multiplication table are sorted in increasing order. It is assumed that $n$ is odd.

For example, the $3 \times 3$ multiplication table is as follows: $$\begin{matrix} 1 & 2 & 3 \\ 2 & 4 & 6 \\ 3 & 6 & 9 \\ \end{matrix}$$ The numbers in increasing order are $[1,2,2,3,3,4,6,6,9]$, so the answer is $3$.

Input

The only input line has an integer $n$.

Output

Print one integer: the answer to the task.

Constraints

• $1 \le n < 10^6$

Example

Input:

3

Output:

3